A Wired Laccase Oxygen Cathode with Carboxylated Single-Walled Carbon Nanotubes Incorporated

The wired laccase cathode with the incorporation of single-walled carbon nanotubes (SWNTs) functionalized with carboxyl groups was constructed. As the wiring redox polymer, the copolymer of polyacrylamide and poly(N-vinylimidazole) complexed with [Os(2,2′;6′2″-terpyridine)(4,4′-dimethyl-2,2′-bipyridine)]^2+/3+ (PAA-PVI-[Os(tpy)(dme-bpy)₂]^2+/3+) was used. The prepared laccase cathode was applied for the electrocatalytic reduction of oxygen. With the addition of the carboxylated carbon nanotubes (CNT-COOHs), in comparison to the result with no CNT-COOHs included, the catalytic O₂ reduction current density increased from 0.35 mA/cm² to 0.59 mA/cm² at the cathode under the condition of a 500 rpm electrode rotation speed in an air-saturated pH 5.0 2.0 M citrate buffer at 37°C. Other effects showing less current decreases with halide ion additions and enhanced stability, when CNT-COOHs were included, were also observed.